Novel integration scheme for breakdown voltage enhancement of a piezoelectric metal-insulator-metal device

ABSTRACT

Various embodiments of the present disclosure are directed towards a piezoelectric metal-insulator-metal (MIM) device including a piezoelectric structure between a top electrode and a bottom electrode. The piezoelectric layer includes a top region overlying a bottom region. Outer sidewalls of the bottom region extend past outer sidewalls of the top region. The outer sidewalls of the top region are aligned with outer sidewalls of the top electrode. The piezoelectric layer is configured to help limit delamination of the top electrode from the piezoelectric layer.

REFERENCE TO RELATED APPLICATION

This Application claims the benefit of U.S. Provisional Application No.62/736,734, filed on Sep. 26, 2018, the contents of which are herebyincorporated by reference in their entirety.

BACKGROUND

Piezoelectric devices (e.g., piezoelectric actuators, piezoelectricsensors, etc.) are used in many modern day electronic devices (e.g.,automotive sensors/actuators, aerospace sensors/actuators, etc.). Oneexample of a piezoelectric device is a piezoelectric actuator. Apiezoelectric actuator can be utilized to create a physical movementthat exerts a force on a physical part in a system under the control ofan electrical signal. The physical movement generated by thepiezoelectric actuator can be utilized to control various kinds ofsystems (e.g., mechanical systems, optical systems, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of some embodiments of ametal-insulator-metal (MIM) capacitor having a piezoelectric structurecomprising a ledge in contact with a passivation layer.

FIG. 2 illustrates a cross-sectional view of a close-up of a first sideof the MIM capacitor of FIG. 1.

FIG. 3 illustrates a cross-sectional view of some alternativeembodiments of the MIM capacitor of FIG. 1.

FIG. 4 illustrates a perspective view of some embodiments of a MIMcapacitor having a piezoelectric structure comprising a ledge in contactwith a passivation layer.

FIG. 5 illustrates a cross-sectional view of some alternativeembodiments of the MIM capacitor of FIG. 1.

FIGS. 6-14 illustrate cross-sectional views of some embodiments offorming a MIM capacitor having a piezoelectric structure comprising aledge in contact with a passivation layer.

FIG. 15 illustrates a methodology in flowchart format that illustratessome embodiments of forming a MIM capacitor having a piezoelectricstructure comprising a ledge in contact with a passivation layer.

DETAILED DESCRIPTION

The present disclosure provides many different embodiments, or examples,for implementing different features of this disclosure. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Some piezoelectric devices include a piezoelectric structure between atop electrode and a bottom electrode referred to as a piezoelectricmetal-insulator-metal (MIM) device. During formation of thepiezoelectric MIM device, a piezoelectric layer is formed over a bottommetal layer and a top metal layer is formed over the piezoelectriclayer. A patterning process is performed on the aforementioned layers todefine the top electrode, the piezoelectric structure, and the bottomelectrode of the piezoelectric MIM device. When a voltage is appliedbetween the top electrode and the bottom electrode, an electrical fieldgenerated by the applied voltage can cause the piezoelectric structureto change from a first shape to a second shape. This change in shape canbe used to control various kinds of systems (e.g., mechanical systems,optical systems, etc.).

A challenge with the above piezoelectric MIM device is premature devicebreakdown due to high physical strain. During operation of thepiezoelectric MIM device a top edge of the top electrode in contact withthe piezoelectric layer collects a high electrical field relative to thebottom electrode or middle area of the top electrode. The highelectrical field at the top edge of the top electrode results in highphysical strain at the top edge while the piezoelectric layer changesshape. This high physical strain causes the top edge to delaminate fromthe piezoelectric layer at a first bias voltage (e.g., a voltage ofapproximately 67 volts) resulting in a premature breakdown (e.g.,breakdown may occur when the top electrode shorts to the bottomelectrode) of the piezoelectric MIM device.

In some embodiments of the present disclosure, an improved method formanufacturing a piezoelectric MIM device that utilizes an over-etchprocess and formation of a passivation layer to mitigate prematuredevice breakdown is provided. The improved method includes forming apiezoelectric layer over a bottom metal layer and forming a top metallayer over the piezoelectric layer. A first patterning process isperformed on the top metal layer to define the top electrode. Whileperforming the first patterning process an over-etch process isperformed and a top region of the piezoelectric layer is patterned aswell. A second patterning process is performed on a bottom region(directly underlying the top region) of the piezoelectric layer todefine the piezoelectric structure. The second patterning processdefines a ledge of the piezoelectric structure such that outer sidewallsof the top region of the piezoelectric structure are laterally offsetfrom outer sidewalls of the bottom region of the piezoelectricstructure. A top edge of the top electrode is in direct contact with atop edge of the top region of the piezoelectric structure. A thirdpatterning process is performed on the bottom metal layer to define thebottom electrode. A passivation layer is formed over the top electrode,piezoelectric structure, and bottom electrode. The passivation layer isconfigured to clamp the top edge of the top electrode to the top regionof the piezoelectric structure such that the improved process mitigatesthe effects of the high physical strain experienced at the top edge ofthe top electrode.

During operation of the piezoelectric MIM device the passivation layeracts as a clamp that prevents the top edge of the top electrode fromdelaminating from the piezoelectric structure, especially under stressedconditions (i.e., high electrical field, high temperatures, and adverseenvironmental conditions). The clamping effect is due to the formationof the ledge in the piezoelectric structure before forming thepassivation layer, this causes the passivation layer to have a straightsegment overlying an interface between the top edge and the passivationstructure. This, in turn, prevents the premature breakdown of thepiezoelectric MIM device and device breakdown may occur at a second biasvoltage (e.g., a voltage of approximately 110 volts) greater than thefirst bias voltage. Further, the top edge of the top electrode may notdelaminate before or during the device breakdown at the second biasvoltage. Therefore, the over-etch and clamping effect from thepassivation layer increases the voltage the piezoelectric MIM device canoperate at before breakdown occurs, thus increasing device performance,reliability, and structural integrity.

Referring to FIG. 1, a cross-sectional view of a piezoelectricmetal-insulator-metal (MIM) device 100 in accordance with someembodiments is provided.

The piezoelectric MIM device 100 includes a bottom electrode 104overlying a substrate 102. A piezoelectric structure 106 is disposedbetween a top electrode 108 and the bottom electrode 104. A passivationlayer 110 overlies the top electrode 108, the piezoelectric structure106, and the bottom electrode 104. A first conductive contact 112overlies the passivation layer 110 and directly contacts the topelectrode 108 on a first side of the piezoelectric MIM device 100. Asecond conductive contact 114 overlies the passivation layer 110 anddirectly contacts the bottom electrode 104. The first and secondconductive contacts 112, 114 are respectively electrically coupled tothe top electrode 108 and the bottom electrode 104.

The piezoelectric structure 106 comprises a top region 106 tr directlyoverlying a bottom region 106 br. The piezoelectric structure 106 is asingle continuous material from a bottom surface of the bottom region106 br to a top surface of the top region 106 tr. In some embodiments,the top region 106 tr is a first piezoelectric material and the bottomregion 106 br is a second piezoelectric material different than thefirst piezoelectric material (not shown). The bottom region 106 brcomprises a first pair of opposing sidewalls 106 bs ₁, 106 bs ₂ and thetop region 106 tr comprises a second pair of opposing sidewalls 106 ts₁, 106 ts ₂. The second pair of opposing sidewalls 106 ts ₁, 106 ts ₂ ofthe top region 106 tr are laterally offset the first pair of opposingsidewalls 106 bs ₁, 106 bs ₂ of the bottom region 106 br by a ledge 1061of the piezoelectric structure 106. The passivation layer 110continuously extends from a top surface of the top electrode 108 acrossthe second pair of opposing sidewalls 106 ts ₁, 106 ts ₂, the ledge1061, and the first pair of opposing sidewalls 106 bs ₁, 106 bs ₂ to atop surface of the bottom electrode 104. The passivation layer 110includes a segment that extends along a straight line from the ledge1061 to the top surface of the top electrode 108 such that thepassivation layer 110 acts as a clamp on an interface 107 between thetop electrode 108 and the piezoelectric structure 106. This, in turn,increases the structural integrity of the top electrode 108 and thepiezoelectric structure 106 at the interface 107.

During operation of the piezoelectric MIM device 100 a voltage isapplied between the top electrode 108 and the bottom electrode 104. Anelectrical field generated by the applied voltage can cause thepiezoelectric structure 106 to change from a first shape to a secondshape (not shown). This change in shape may be used to control variouskinds of systems (e.g., mechanical systems, optical systems, etc.).Further, the change in shape results in mechanical stress on thepiezoelectric MIM device 100 especially as the applied voltageincreases. As the applied voltage increases, for example, to a firstbias voltage (e.g., a voltage within a range of approximately 67-109volts) a high local electrical field will collect at a top edge of thetop electrode 108 at the interface 107. The high local electrical fieldcauses the top edge of the top electrode 108 to be susceptible todelamination. However, the shape of the passivation layer 110 over thetop electrode 108 and the piezoelectric structure 106 is configured toclamp the top edge of the top electrode 108 to the piezoelectricstructure 106 at the interface 107. This, in turn, prevents delaminationof the top electrode 108 at the first bias voltage. Further, as theapplied voltage reaches a break down bias voltage (e.g., approximately110 volts or greater), the breakdown may not occur at the top edge ofthe top electrode 108, but instead at a different location. Therefore,the clamp effect of the passivation layer 110 at the interface 107increases the structural integrity, voltage operation range, andreliability of the piezoelectric MIM device 100.

Referring to FIG. 2, some embodiments of a cross-sectional view 200 of aportion of the piezoelectric MIM device 100 of FIG. 1, as indicated bythe dashed outline box shown in FIG. 1 is provided.

As seen in the cross-sectional view 200 a plurality of angles, lengthsand thicknesses are labeled. Unless otherwise stated, an angle in theplurality of angles is defined relative to a flat horizontal line. Asidewall of the top electrode 108 is angled at a non-zero top electrodesidewall angle θ_(te) relative to a flat horizontal line extendingacross a bottom surface of the top electrode 108. A first outer sidewall106 ts ₂ of the top region 106 tr is angled at a non-zero top regionsidewall angle θ_(tr) relative to a ledge 1061. In some embodiments, thetop electrode sidewall angle θ_(te) and the top region sidewall angleθ_(tr) are equal. In some embodiments, the top electrode sidewall angleθ_(tr) and the top region sidewall angle θ_(tr) may, for example, bewithin a range of approximately 90 to 170 degrees. A first outersidewall 106 bs ₂ of the bottom region 106 br is angled at a non-zerobottom region sidewall angle θ_(br) relative to a top surface of thebottom electrode 104. In some embodiments, the bottom region sidewallangle θ_(br) may, for example, be within a range of approximately 90 to170 degrees. A sidewall of the bottom electrode 104 is angled at anon-zero bottom electrode sidewall angle θ_(be) relative to a topsurface of the substrate 102. In some embodiments, the bottom electrodesidewall angle θ_(be) may, for example, be within a range ofapproximately 90 to 170 degrees. While the respective opposing sidewallof each sidewall referenced above is not shown in cross-sectional view200, it may be appreciated that the respective opposing sidewallillustrated in FIG. 1 of each sidewall referenced above has the samesidewall angle. For example, a second outer sidewall (106 ts ₁ ofFIG. 1) of the top region 106 tr is angled at the non-zero top regionsidewall angle θ_(tr) relative to the ledge 1061.

In some embodiments, a thickness T_(tr) of the top region is within arange of approximately 1 to 4 Angstroms, 10 to 400 Angstroms, 0.1 to 0.4micrometers, 1 to 40 micrometers, or 100 to 400 micrometers. In someembodiments, the thickness T_(tr) of the top region 106 tr is at leasthalf as thick as the bottom region 106 br. In some embodiments, athickness of the bottom region 106 br is within a range of 2 to 10 timesgreater than the thickness T_(tr) of the top region 106 tr. In someembodiments, if the thickness of the bottom region 106 br is, forexample, greater than 10 times thicker than the thickness T_(tr) of thetop region 106 tr, the passivation layer 110 may be unable toeffectively clamp the top electrode 108 to the top region 106 tr anddelamination at the interface 107 may occur. In some embodiments, alength L₁ of the ledge 1061 is within a range of approximately 5 to 100Angstroms, 50 to 1000 Angstroms, 0.05 to 1 micrometers, 0.5 to 100micrometers, or 50 to 1000 micrometers. In some embodiments, a lengthL_(ts) of a segment of a top surface of the bottom electrode 104 betweena lower bottom edge of the bottom region 106 tr and a top edge of thebottom electrode 104 is within a range of approximately 10 to 100Angstroms, 100 to 1000 Angstroms, 0.1 to 1 micrometers, 1 to 100micrometers, or 100 to 1000 micrometers. In some embodiments, the lengthL_(ts) of the segment of the top surface of the bottom electrode 104 iswithin a range of 0.5 to 10 times greater than the length L₁ of theledge 1061. In some embodiments, if the length L₁ of the ledge 1061 is,for example, too small (e.g., less than 5 Angstroms) then thepassivation layer 110 may not have a proper shape over the interface107.

With reference to FIG. 3, a cross-sectional view of a piezoelectric MIMdevice 300 according to some alternative embodiments of thepiezoelectric MIM device 100 of FIG. 1 is provided in which outersidewalls of the top electrode 108, top region 106 tr, bottom region 106br, and bottom electrode 104 are respectively vertical.

Outer sidewalls of the top electrode 108 are respectively angled by atop electrode sidewall angle θ_(te) (e.g., 90 degrees) relative to aflat horizontal line extending across a bottom surface of the topelectrode 108. The top region 106 tr comprises the second pair ofopposing sidewalls 106 ts ₁, 106 ts ₂ respectively angled by a topregion sidewall angle θ_(tr) (e.g., 90 degrees) relative to the ledge1061. The bottom region 106 br comprises the first pair of opposingsidewalls 106 bs ₁, 106 bs ₂ respectively angled by a bottom regionsidewall angle θ_(br) (e.g., 90 degrees) relative to a top surface ofthe bottom electrode 104. Outer sidewalls of the bottom electrode 104are respectively angled by a bottom electrode sidewall angle θ_(be)(e.g., 90 degrees) relative to a top surface of the substrate 102.Therefore, the aforementioned sidewalls outlined above are angled at asame angle value (i.e., 90 degrees). In some embodiments, theaforementioned sidewalls outlined above are angled at the same anglevalue such as, for example, 100 degrees, 135 degrees, or a value withina range of approximately 90 to 170 degrees.

With reference to FIG. 4, a perspective view of a piezoelectric MIMdevice 400 according to some alternative embodiments of thepiezoelectric MIM device 100 of FIG. 1 is provided.

The piezoelectric MIM device 400 includes a substrate 102 below a bottomelectrode 104. A piezoelectric structure 106 overlies the bottomelectrode 104. The piezoelectric structure 106 comprises a top region106 tr directly overlying a bottom region 106 br. A top electrode 108overlies the piezoelectric structure 106 such that outer sidewalls ofthe top electrode 108 are aligned with outer sidewalls of the top region106 tr. A passivation layer 110 overlies the top electrode 108, thepiezoelectric structure 106, the bottom electrode 104, and the substrate102. A first conductive contact 112 overlies the passivation layer 110and directly contacts the top electrode 108. A second conductive contact114 overlies the passivation layer 110 and directly contacts the bottomelectrode 104. The first and second conductive contacts 112, 114 arerespectively electrically coupled to the top electrode 108 and thebottom electrode 104. During operation of the piezoelectric MIM device400 a bias voltage is applied between the first and second conductivecontacts 112, 114.

The passivation layer 110 is configured to clamp the top electrode 108to the top region 106 tr of the piezoelectric structure 106 at aninterface 107. The passivation layer 110 directly contacts outersidewalls of the top electrode 108, outer sidewalls of the top region106 tr, outer sidewalls of the bottom region 106 br, and outer sidewallsof the bottom electrode 104. The passivation layer extends continuouslyfrom a top surface of the top electrode 108 to a top surface of thesubstrate 102.

With reference to FIG. 5, a cross-sectional view of some embodiments ofan integrated chip 500 including the piezoelectric MIM device 100 ofFIG. 1 is provided in which the first and second conductive contacts112, 114 are respectively wired bonded to metal lines 504 disposedwithin a printed circuit board (PCB) substrate 502.

The integrated chip 500 includes the piezoelectric MIM device 100overlying the PCB substrate 502. A bottom electrode 104 overlies the PCBsubstrate 502. A piezoelectric structure 106 overlies the bottomelectrode 104. The piezoelectric structure 106 comprises a top region106 tr directly overlying a bottom region 106 br. A maximum width of thetop region 106 tr is less than a minimum width of the bottom region 106br. A top electrode 108 overlies the piezoelectric structure 106 suchthat outer sidewalls of the top electrode 108 are aligned with outersidewalls of the top region 106 tr. A passivation layer 110 overlies thetop electrode 108, the piezoelectric structure 106, the bottom electrode104, and the substrate 102. A first conductive contact 112 overlies thepassivation layer 110 and directly contacts the top electrode 108 on afirst side of the piezoelectric MIM device 100. A second conductivecontact 114 overlies the passivation layer 110 and directly contacts thebottom electrode 104. The first and second conductive contacts 112, 114are respectively electrically coupled to the top electrode 108 and thebottom electrode 104.

The PCB substrate 502 comprises the metal lines 504. Electricalconnector pads 504 a respectively overlie the metal lines 504. A firstsolder ball 508 a overlies the first conductive contact 112. A secondsolder ball 508 b overlies the second conductive contact 114. The firstand second solder balls 508 a, 508 b provide contacts points forconductive wires 506. The conductive wires 506 directly contact themetal lines 504 and the connector pads 504 a. In some embodiments, theconductive wires 506 are electrically coupled to a different independentdevice (not shown). In some embodiments, the metal lines 504 areelectrically coupled to electronic devices (e.g., transistors,resistors, capacitors, varactors, etc.) through a back end of line(BEOL) interconnect structure underlying the metal lines 504 (notshown).

In some embodiments, the passivation layer 110 may, for example, be orcomprise ceramic, metal oxide, carbide, silicon oxide, nitride, or thelike formed to a thickness within a range of approximately 1000 to 3000Angstroms. In some embodiments, if the passivation layer 110 is formedto a thickness less than approximately 1000 Angstroms, the piezoelectricMIM device 100 may have insufficient structural integrity. This, inturn, may result in premature breakdown at a bias voltage (e.g., 67volts) less than approximately 110 volts. In some embodiments, if thepassivation layer 110 is formed to a thickness greater thanapproximately 3000 Angstroms, the piezoelectric MIM device 100 may haveincreased structural integrity but device performance will be degraded(e.g., when the piezoelectric MIM device 100 is configured as anactuator). This, in turn, may mitigate the change in shape thepiezoelectric structure 106 may undergo.

In some embodiments, the top electrode 108 and the bottom electrode 104may, for example, be or comprise stainless steel, brass, copper,galvanized iron, lead, monel, nickel, nickel-chromium, zinc, bronze,aluminum, platinum, gold, ruthenium, graphite, calcium, lithiumfluoride, molybdenum(VI) oxide, silver, palladium, Tin, scandium,titanium, vanadium, chromium, manganese, cobalt, gallium, indium,thallium, doped silicon, polysilicon, germanium, antimony, tungsten,hafnium, iridium, mixed metal oxide, titanium nitride, tantalum nitride,or the like. In some embodiments, the top electrode 108 and/or thebottom electrode 104 may, for example, be formed to a thickness within arange of approximately 10 to 100 Angstroms, 100 to 1000 Angstroms, 0.1to 1 micrometers, 1 to 100 micrometers, or 100 to 1000 micrometers. Insome embodiments, the piezoelectric structure 106 may, for example, beor comprise a piezoelectric material, aluminum nitride, lead zirconatetitanate (e.g., Pb[Zr_(x)Ti_(1-x)]O₃, where x is a suitable positivenumber), zinc oxide, or the like formed to a thickness within a range ofapproximately 10 to 100 Angstroms, 100 to 1000 Angstroms, 0.1 to 1micrometers, 1 to 100 micrometers, or 100 to 1000 micrometers.

FIGS. 6-14 illustrate cross-sectional views 600-1400 of some embodimentsof a method of forming a piezoelectric metal-insulator-metal (MIM)device according to the present disclosure. Although the cross-sectionalviews 600-1400 shown in FIGS. 6-14 are described with reference to amethod, it will be appreciated that the structures shown in FIGS. 6-14are not limited to the method but rather may stand alone separate of themethod. Although FIGS. 6-14 are described as a series of acts, it willbe appreciated that these acts are not limiting in that the order of theacts can be altered in other embodiments, and the methods disclosed arealso applicable to other structures.

As shown in cross-sectional view 600 of FIG. 6, a substrate 102 isprovided. A bottom metal layer 602 is formed over the substrate 102. Apiezoelectric layer 604 is formed over the bottom metal layer 602. A topmetal layer 606 is formed over the piezoelectric layer 604. A firstmasking layer 608 is formed over the top metal layer 606. The firstmasking layer 608 has a length L_(m1) defined between outer sidewalls ofthe first masking layer 608.

As shown in cross-sectional view 700 of FIG. 7, a first patterningprocess is performed on the structure of FIG. 6 according to the firstmasking layer 608. In some embodiments, the first patterning processremoves an entire thickness of the top metal layer (606 of FIG. 6)laterally offset outer sidewalls of the first masking layer 608, therebydefining a top electrode 108. An etching process is used to define thetop electrode 108 and over-etches into the piezoelectric layer 604 todefine a top region of the piezoelectric layer 604. In some embodiments,the top metal layer (606 of FIG. 6) and the top region of thepiezoelectric layer 604 are etched by a single etchant in a singleetching process. Outer sidewalls of the top electrode 108 are alignedwith outer sidewalls of the top region. The outer sidewalls of the topelectrode 108 are respectively angled by a top electrode sidewall angleθ_(te) relative to a flat horizontal line extending across a bottomsurface of the top electrode 108. The outer sidewalls of the top regionare respectively angled by a top region sidewall angle θ_(tr) relativeto a straight horizontal line aligned with a bottom surface of the topregion. In some embodiments, the first patterning process includes a lowselectivity dry etch, but other etch processes are amendable. A removalprocess is performed to remove the first masking layer 608 (not shown).

In further embodiments, the first patterning process includes performinga dry etch process (e.g., an ion-beam etch process). In suchembodiments, the dry etch process may be performed at a non-zero anglerelative to a substantially vertical line that is perpendicular to a topsurface of the substrate 102. In such embodiments, the angle of the dryetch process may be set to define the top electrode sidewall angleθ_(te) and/or the top region sidewall angle θ_(tr). Additionally, thedry etch process is performed in such a manner that outer sidewalls ofthe top electrode 108 and sidewalls of the piezoelectric layer 604 aresubstantially aligned. This may be due to the low selectivity dry etchand/or the angle the dry etch process is performed at. In yet furtherembodiments, the first patterning process may form an undercut profilein the top electrode 108, wherein outer sidewalls of the top electrode108 are spaced laterally between outer sidewalls of the first maskinglayer 608.

As shown in cross-sectional view 800 of FIG. 8, a second masking layer802 is formed over the top electrode 108 and the piezoelectric layer604. The second masking layer 802 has a length L_(m2) defined betweenouter sidewalls of the second masking layer 802. In some embodiments,the length L_(m1) of the first masking layer (608 of FIG. 6) is lessthan the length L_(m2) of the second masking layer 802. In someembodiments, the second masking layer 802 is configured to protect theouter sidewalls of the top electrode 108 and sidewalls of thepiezoelectric layer 604 during subsequent processing steps (e.g., thesecond patterning process of FIG. 9). Further, the second masking layer802 is configured to define and/or protect the ledge (1061 of FIG. 9) ofthe piezoelectric structure (106 of FIG. 9).

As shown in cross-sectional view 900 of FIG. 9, a second patterningprocess is performed on the structure of FIG. 8 according to the secondmasking layer (802 of FIG. 8). The second patterning process removes anentire thickness of the piezoelectric layer (604 of FIG. 8) laterallyoffset outer sidewall of the second masking layer (802 of FIG. 8)defining a piezoelectric structure 106. The second patterning processdefines a bottom region of the piezoelectric structure 106 directlyunderlying the top region of the piezoelectric structure 106 and a ledge1061 of the piezoelectric layer 106. Outer sidewalls of the top regionare laterally offset outer sidewalls of the bottom region by the ledge1061. In some embodiments, a length L₁ of the ledge 1061 is within arange of approximately 5 to 100 Angstroms, 50 to 1000 Angstroms, 0.05 to1 micrometers, 0.5 to 100 micrometers, or 50 to 1000 micrometers. Theouter sidewalls of the bottom region of the piezoelectric structure 106are respectively angled by a bottom region sidewall angle θ_(br)relative to a top surface of the bottom metal layer 602. In someembodiments, the second patterning process includes a low selectivitydry etch, but other etch processes are amendable. The top regionsidewall angle θ_(tr), ledge 1061, and bottom region angle θ_(br) helpto clamp the top electrode 106 to the piezoelectric structure 106 andthe bottom metal layer 602, so as to help limit delamination.

As shown in cross-sectional view 1000 of FIG. 10, a third masking layer1002 is formed over the top electrode 108, the piezoelectric structure106, and the bottom metal layer 602. A midpoint 1002 mp of the thirdmasking layer 1002 is laterally offset a midpoint 108 mp of the topelectrode 108 and the piezoelectric structure 106. In some embodiments,the midpoint 1002 mp of the third masking layer 1002 is verticallyaligned with the midpoint 108 mp of the top electrode 108 and a midpointof the piezoelectric structure 106 (not shown). The third masking layer1002 has a length L_(m3) defined between outer sidewalls of the thirdmasking layer 1002. In some embodiments, the second length L_(m2) of thesecond masking layer (802 of FIG. 8) is less than the length L_(m3) ofthe third masking layer 1002. In such embodiments, the length L_(m3) isgreater than the length L_(m1) of the first masking layer (608 of FIG.6). In some embodiments, a size of the third masking layer 1002 isgreater than a size of the second masking layer (802 of FIG. 8), and thesize of the second masking layer (802 of FIG. 8) is greater than a sizeof the first masking layer (608 of FIG. 6). In further embodiments, aheight of the third masking layer 1002 is greater than a height of thesecond masking layer (802 of FIG. 8), and the height of the secondmasking layer (802 of FIG. 8) is greater than a height of the firstmasking layer (608 of FIG. 6). The third masking layer 1002 isconfigured to protect the outer sidewalls of the top electrode 108,sidewalls of the piezoelectric structure 106, and/or the ledge (1061 ofFIG. 9) of the piezoelectric structure 106 from subsequent processingsteps (e.g., the third patterning process of FIG. 11).

As shown in cross-sectional view 1100 of FIG. 11, a third patterningprocess is performed on the structure of FIG. 10 according to the thirdmasking layer (1002 of FIG. 10). The third pattering process removes anentire thickness of the bottom metal layer (602 of FIG. 10) laterallyoffset outer sidewalls of the third masking layer (1002 of FIG. 10)defining a bottom electrode 104. In some embodiments, a length L_(fs) ofa segment of the bottom electrode 104 on a first side 104 a between afirst outer sidewall of the bottom region of the piezoelectric structure106 and a first top edge of the bottom electrode 104 is within a rangeof approximately 1 to 25 Angstroms, 1 to 250 Angstroms, 0.01 to 0.25micrometers, 0.1 to 25 micrometers, or 10 to 250 micrometers. In someembodiments, a length L_(ts) of a segment of the bottom electrode 104 ona second side 104 b between a second outer sidewall of the bottom regionof the piezoelectric structure 106 and a second top edge of the bottomelectrode 104 is within a range of approximately 10 to 100 Angstroms,100 to 1000 Angstroms, 0.1 to 1 micrometers, 1 to 100 micrometers, or100 to 1000 micrometers. In some embodiments, the length L_(ts) of thesegment of the bottom electrode 104 on the second side 104 b is within arange of 2 to 10 times greater than the length L_(fs) of the segment ofthe bottom electrode 104 on the first side 104 a. Outer sidewalls of thebottom electrode 104 are respectively angled by a bottom electrodesidewall angle θ_(be) relative to a top surface of the substrate 102.

As shown in cross-sectional view 1200 of FIG. 12, a passivation layer110 is formed over the top electrode 108, the piezoelectric structure106, the bottom electrode 104, and the substrate 102 define apiezoelectric MIM device 100. In some embodiments, the passivation layer110 may, for example, be or comprise ceramic, metal oxide, carbide,silicon oxide, nitride, or the like formed to a thickness within a rangeof approximately 1000 to 3000 Angstroms. In some embodiments, if thepassivation layer 110 is formed to a thickness less than approximately1000 Angstroms, the piezoelectric MIM device 100 may exhibit prematurebreakdown at a bias voltage (e.g., 67 volts) less than approximately 110volts during operation of the piezoelectric MIM device 100. In someembodiments, if the passivation layer 110 is formed to a thicknessgreater than approximately 3000 Angstroms, the piezoelectric MIM device100 may have increased structural integrity but device performance willbe degraded (e.g., when the piezoelectric MIM device 100 is configuredas an actuator). This, in turn, may mitigate the change in shape thepiezoelectric structure 106 may undergo.

As shown in cross-sectional view 1300 of FIG. 13, the passivation layer110 is patterned forming a first opening 1302 above a top surface of thetop electrode 108 and forming a second opening 1304 above a top surfaceof the bottom electrode 104.

As shown in cross-sectional view 1400 of FIG. 14, a first conductivecontact 112 is formed over the passivation layer 110 and the topelectrode 108. The first conductive contact 112 directly contacts thetop surface of the top electrode 108 and fills the first opening (1302of FIG. 13). A second conductive contact 114 is formed over thepassivation layer 110 and the bottom electrode 104. The secondconductive contact 114 directly contacts the top surface of the bottomelectrode 108 and fills the second opening (1304 of FIG. 13). In someembodiments, the first and second conductive contacts 112, 114 may, forexample, be or comprise copper, aluminum, or the like. In someembodiments the first and second conductive contacts 112, 114 arecomprised of a conductive material different than a material of the topelectrode 108 and/or the bottom electrode 104.

FIG. 15 illustrates a method 1500 of forming a piezoelectricmetal-insulator-metal (MIM) device in accordance with some embodiments.Although the method 1500 is illustrated and/or described as a series ofacts or events, it will be appreciated that the method is not limited tothe illustrated ordering or acts. Thus, in some embodiments, the actsmay be carried out in different orders than illustrated, and/or may becarried out concurrently. Further, in some embodiments, the illustratedacts or events may be subdivided into multiple acts or events, which maybe carried out at separate times or concurrently with other acts orsub-acts. In some embodiments, some illustrated acts or events may beomitted, and other un-illustrated acts or events may be included.

At 1502, a bottom electrode is formed over a substrate. FIG. 6illustrates a cross-sectional view 600 corresponding to some embodimentsof act 1502.

At 1504, a piezoelectric layer is formed over the bottom electrode, thepiezoelectric layer includes a top region overlying a bottom region.FIG. 6 illustrates a cross-sectional view 600 corresponding to someembodiments of act 1504.

At 1506, a top electrode is formed over the piezoelectric layer. FIG. 6illustrates a cross-sectional view 600 corresponding to some embodimentsof act 1506.

At 1508, a first patterning process is performed on the top electrodeand the top region of the piezoelectric layer according to a firstmasking layer. FIGS. 6 and 7 illustrate cross-sectional views 600 and700 corresponding to some embodiments of act 1508.

At 1510, a second patterning process is performed on the bottom regionof the piezoelectric layer according to a second masking layer. FIGS. 8and 9 illustrate cross-sectional views 800 and 900 corresponding to someembodiments of act 1510.

At 1512, a third patterning process is performed on the bottom electrodeaccording to a third masking layer. FIGS. 10 and 11 illustratecross-sectional views 1000 and 1100 corresponding to some embodiments ofact 1512.

At 1514, a passivation layer is formed over the top electrode, thepiezoelectric layer, and the bottom electrode. FIG. 12 illustrates across-sectional view 1200 corresponding to some embodiments of act 1514.

At 1516, an etch process is performed on the passivation layer to form afirst opening over the top electrode and a second opening over thebottom electrode. FIG. 13 illustrates a cross-sectional view 1300corresponding to some embodiments of act 1516.

At 1518, a first electrical contact is formed directly over the topelectrode and a second electrical contact is formed directly over thebottom electrode. FIG. 14 illustrates a cross-sectional view 1400corresponding to some embodiments of act 1518.

Accordingly, in some embodiments, the present disclosure relates to amethod of forming a piezoelectric MIM device that includes a passivationlayer configured to clamp a top electrode to a piezoelectric structure.

In some embodiments, the present application provides a piezoelectricdevice including: a bottom electrode; a top electrode overlying thebottom electrode; and a piezoelectric layer disposed between the bottomelectrode and the top electrode, wherein the piezoelectric layercomprises a top region overlying a bottom region, outer sidewalls of thebottom region extend past outer sidewalls of the top region, wherein theouter sidewalls of the top region are aligned with outer sidewalls ofthe top electrode.

In some embodiments, the present application provides ametal-insulator-metal (MIM) device, including: a semiconductorsubstrate; a bottom electrode overlying the semiconductor substrate; atop electrode overlying the bottom electrode; a passivation layeroverlying the top electrode; and a piezoelectric structure between thetop electrode and the bottom electrode, wherein the piezoelectricstructure comprises a first outer sidewall facing a first direction anda second outer sidewall facing the first direction, wherein the firstouter sidewall is laterally offset the second outer sidewall by a ledgeof the piezoelectric structure extending from the first outer sidewallto the second outer sidewall, and wherein the ledge of the piezoelectricstructure is in direct contact with the passivation layer.

In some embodiments, the present application provides a method forforming a metal-insulator-metal (MIM) structure, the method including:forming a bottom electrode over a substrate; forming a piezoelectriclayer over the bottom electrode, wherein the piezoelectric layercomprises a top region overlying a bottom region; forming a topelectrode over the piezoelectric layer; performing a first patterningprocess on the top electrode and the top region of the piezoelectriclayer according to a first masking layer; performing a second patterningprocess on the bottom region of the piezoelectric layer according to asecond masking layer, wherein a size of the second masking layer isgreater than a size of the first masking layer; performing a thirdpatterning process on the bottom electrode according to a third maskinglayer, wherein a size of the third masking layer is greater than thesize of the second masking layer; and forming a passivation layer overthe top electrode, piezoelectric layer, and the bottom electrode.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A piezoelectric device comprising: a bottom electrode; a topelectrode overlying the bottom electrode; and a piezoelectric layerdisposed between the bottom electrode and the top electrode, wherein thepiezoelectric layer comprises a top region overlying a bottom region,outer sidewalls of the bottom region extend past outer sidewalls of thetop region, wherein the outer sidewalls of the top region are alignedwith outer sidewalls of the top electrode.
 2. The piezoelectric deviceof claim 1, further comprising: a passivation layer overlying the topelectrode and the piezoelectric layer, wherein the passivation layercontinuously extends from the bottom region across outer sidewalls ofthe top region to an upper surface of the top electrode; and metalcontacts extending through the passivation layer to the top electrodeand the bottom electrode, respectively.
 3. The piezoelectric device ofclaim 2, wherein an outer sidewall of the bottom region is laterallyoffset from an outer sidewall of the bottom electrode by an upper ledgeof the bottom electrode, wherein the upper ledge of the bottom electrodeis in direct contact with the passivation layer.
 4. The piezoelectricdevice of claim 3, wherein an outer sidewall of the top electrode islaterally offset from the outer sidewall of the bottom region by anupper ledge of the bottom region, wherein the upper ledge of the bottomregion is in direct contact with the passivation layer.
 5. Thepiezoelectric device of claim 4, wherein the upper ledge of the bottomelectrode is longer than the upper ledge of the bottom region.
 6. Thepiezoelectric device of claim 1, wherein outer sidewalls of the topelectrode and the outer sidewalls of the top region are aligned.
 7. Thepiezoelectric device of claim 6, wherein the outer sidewalls of the topelectrode slant laterally in opposite directions, wherein the outersidewalls of the top region slant laterally in opposite directions. 8.The piezoelectric device of claim 1, wherein outer sidewalls of the topelectrode and the outer sidewalls of the top region slant at a firstangle relative to a line perpendicular to a bottom surface of thepiezoelectric layer, wherein the outer sidewalls of the bottom regionslant at a second angle relative to the line perpendicular to the bottomsurface of the piezoelectric layer, wherein the first angle is differentthan the second angle.
 9. The piezoelectric device of claim 1, wherein athickness of the bottom region is at least two times greater than athickness of the top region, and wherein the top and bottom regions area same material.
 10. A metal-insulator-metal (MIM) device, comprising: asemiconductor substrate; a bottom electrode overlying the semiconductorsubstrate; a top electrode overlying the bottom electrode; a passivationlayer overlying the top electrode; and a piezoelectric structure betweenthe top electrode and the bottom electrode, wherein the piezoelectricstructure comprises a first outer sidewall facing a first direction anda second outer sidewall facing the first direction, wherein the firstouter sidewall is laterally offset the second outer sidewall by a ledgeof the piezoelectric structure extending from the first outer sidewallto the second outer sidewall, and wherein the ledge of the piezoelectricstructure is in direct contact with the passivation layer.
 11. The MIMdevice of claim 10, wherein the passivation layer extends continuouslyfrom a top surface of the top electrode to a top surface of the bottomelectrode, wherein the passivation layer directly contacts an outersidewall of the top electrode, the first and second outer sidewalls ofthe piezoelectric structure, and the ledge of the piezoelectricstructure, wherein the outer sidewall of the top electrode faces thefirst direction.
 12. The MIM device of claim 11, wherein the first outersidewall and the outer sidewall of the top electrode are aligned suchthat a segment of the passivation layer directly contacting the firstouter sidewall and the outer sidewall of the top electrode is definedalong a straight line.
 13. The MIM device of claim 10, wherein thesecond outer sidewall is laterally offset an outer sidewall of thebottom electrode by a ledge of the bottom electrode, wherein the ledgeof the bottom electrode at least partially defines an uppermost surfaceof the bottom electrode, and wherein the outer sidewall of the bottomelectrode faces the first direction.
 14. The MIM device of claim 13,wherein the ledge of the bottom electrode is at least two times longerthan the ledge of the piezoelectric structure.
 15. The MIM device ofclaim 10, wherein a width of the piezoelectric structure continuouslydecreases from a top surface of the bottom electrode to the ledge of thepiezoelectric structure, wherein the width of the piezoelectricstructure continuously decreases from the ledge of the piezoelectricstructure to a bottom surface of the top electrode.
 16. The MIM deviceof claim 15, wherein the width of the piezoelectric structure discretelyincreases between the top electrode and the bottom electrode at theledge of the piezoelectric structure.
 17. A method for forming ametal-insulator-metal (MIM) structure, comprising: forming a bottomelectrode over a substrate; forming a piezoelectric layer over thebottom electrode, wherein the piezoelectric layer comprises a top regionoverlying a bottom region; forming a top electrode over thepiezoelectric layer; performing a first patterning process on the topelectrode and the top region of the piezoelectric layer according to afirst masking layer; performing a second patterning process on thebottom region of the piezoelectric layer according to a second maskinglayer, wherein a size of the second masking layer is greater than a sizeof the first masking layer; performing a third patterning process on thebottom electrode according to a third masking layer, wherein a size ofthe third masking layer is greater than the size of the second maskinglayer; and forming a passivation layer over the top electrode,piezoelectric layer, and the bottom electrode.
 18. The method of claim17, further comprising: performing an etch process on the passivationlayer to form a first opening over the top electrode and a secondopening over the bottom electrode; and forming a first electricalcontact directly over the top electrode and a second electrical contactdirectly over the bottom electrode.
 19. The method of claim 17, whereinthe second patterning process forms a ledge on the bottom region of thepiezoelectric layer.
 20. The method of claim 19, wherein outer sidewallsof the top region are laterally offset outer sidewalls of the bottomregion by the ledge.